mm: nommu: check the vma list when unmapping file-mapped vma

Now we have the sorted vma list, use it in do_munmap() to check that we
have an exact match.
Signed-off-by: NNamhyung Kim <namhyung@gmail.com>
Acked-by: NGreg Ungerer <gerg@uclinux.org>
Cc: David Howells <dhowells@redhat.com>
Cc: Paul Mundt <lethal@linux-sh.org>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

mm/nommu.c

@@ -1635,7 +1635,6 @@ static int shrink_vma(struct mm_struct *mm,
 int do_munmap(struct mm_struct *mm, unsigned long start, size_t len)
 {
 	struct vm_area_struct *vma;
-	struct rb_node *rb;
 	unsigned long end = start + len;
 	int ret;
 
@@ -1668,9 +1667,8 @@ int do_munmap(struct mm_struct *mm, unsigned long start, size_t len)
 			}
 			if (end == vma->vm_end)
 				goto erase_whole_vma;
-			rb = rb_next(&vma->vm_rb);
-			vma = rb_entry(rb, struct vm_area_struct, vm_rb);
-		} while (rb);
+			vma = vma->vm_next;
+		} while (vma);
 		kleave(" = -EINVAL [split file]");
 		return -EINVAL;
 	} else {